© 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.In this study, a Schottky diode was produced on a p-type Si semiconductor using Fe69Ni27Mn4 (wt%) alloy. Scanning electron microscopy, X-ray diffraction, and differential scanning calorimeter measurements were performed to examine the structural, crystallographic, and thermal properties of the alloy. Current–Voltage (I–V) and capacitance–voltage (C–V) techniques were used to investigate the electrical properties of the diode. The basic electrical parameters such as the ideality factor of the diode, the barrier height, and the series resistance of the structure were calculated at different illumination intensities. It was observed that these values differ depending on the light intensity. Experimental results showed that series resistance and interface states depend on frequency and light intensity. The C–V plots display anomalous peak behavior. Bu result showed that the diode exhibits negative capacitance (NC) behavior. From the C–V and G/ω–V curves, for all frequencies, the intensity of the NC decreases with increasing frequency and the minimum C value corresponds to the maximum G/ω value. According to all presently obtained characteristics, Fe–Ni–Mn/p-Si diode exhibits Schottky and photodiode behavior. So, the produced diode can be used as a sensor in optoelectronic applications.